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Commit 423bec43 authored by Nishanth Aravamudan's avatar Nishanth Aravamudan Committed by Linus Torvalds
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Documentation: correct overcommit caveat in hugetlbpage.txt 



As shown by Gurudas Pai recently, we can put hugepages into the surplus
state (by echo 0 > /proc/sys/vm/nr_hugepages), even when
/proc/sys/vm/nr_overcommit_hugepages is 0. This is actually correct, to
allow the original goal (shrink the static pool to 0) to succeed (we are
converting hugepages to surplus because they are in use). However, the
documentation does not accurately reflect this case. Update it.

Signed-off-by: default avatarNishanth Aravamudan <nacc@us.ibm.com>
Acked-by: default avatarAndy Whitcroft <apw@shadowen.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 91446b06

Documentation/vm/hugetlbpage.txt

+3 −4
Original line number Diff line number Diff line
@@ -88,10 +88,9 @@ hugepages from the buddy allocator, if the normal pool is exhausted. As 
these surplus hugepages go out of use, they are freed back to the buddy

allocator.



Caveat: Shrinking the pool via nr_hugepages while a surplus is in effect

will allow the number of surplus huge pages to exceed the overcommit

value, as the pool hugepages (which must have been in use for a surplus

hugepages to be allocated) will become surplus hugepages.  As long as

Caveat: Shrinking the pool via nr_hugepages such that it becomes less

than the number of hugepages in use will convert the balance to surplus

huge pages even if it would exceed the overcommit value.  As long as

this condition holds, however, no more surplus huge pages will be

allowed on the system until one of the two sysctls are increased

sufficiently, or the surplus huge pages go out of use and are freed.